Performance evaluation of multi-walled carbon nanotubes for decolorization of synthetic industrial wastewater: equilibrium, kinetics, and thermodynamics

In this study, the application of multi-walled carbon nanotubes (MWCNTs) for the decolorization of synthetic industrial wastewater was assessed. This experimental research was conducted on a laboratory scale using a discontinuous system. The effects of pH, initial dye concentration, a dosage of MWCNTs adsorbent, temperature, and reaction time on the removal of reactive yellow 15 (RY 15) and reactive yellow 42 (RY 42) were investigated. Experimental results showed that the pH value of 3 was optimum for the removal of the dyes by the MWCNTs. The maximum adsorption capacity of 147.85 and 171.6 mg/g were obtained for RY 15 and RY 42, respectively at an initial dye concentration of 50 mg/L and adsorbent concentration of 0.2 g/L. Moreover, the equilibrium data for the adsorption of RY 15 and RY 42 by the MWCNTs followed the Langmuir isotherm. Results indicated that the RY 42 and RY 15 adsorption by MWCNTs followed the pseudo-second-order kinetic model. Furthermore, the adsorption of RY 15 and RY 42 onto MWCNTs was an endothermic reaction. MWCNTs are cost-effective and readily available, therefore, these materials could be used as an efficient adsorbent for the removal of RY 15 and RY 42 dyes from an aqueous solution.